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Apex Predators of Costa Rica: A Survey of Current Knowledge Trisha Stull Mentor: Michael Mooring Committee members: David Cummings, Bob Wiese Abstract pex predators play a critical ecological role in the Neotropics, however they face a range of threats including habitat loss, fragmentation, illegal hunting, and retaliatory killing. The decline of these top predators has been associated with loss of biodiversity, trophic cascades of herbivore and plant populations, a decline in mammalian fauna known as the ‘empty forest syndrome’, and ecological meltdowns. Costa Rica is of particular importance for apex predators as it represents a bottleneck through which northern and southern populations are connected. There are dozens of biological corridors in Costa Rica that aim to promote the movement of fauna between protected areas and forest fragments. Information on the local status of predator populations is required to make informed decisions about conservation actions, but such information is often lacking or difficult to find. There are few published journal articles on this topic, and most studies are in the form of technical reports or masters theses (‘grey literature’) which can be hard to access. The purpose of this project was to construct a centralized database containing the current knowledge regarding mammalian predators in this region. Most of the reports were from the southern half of Costa Rica, with several studies from the Talamanca region and Corcovado National Park. Only Guanacaste and Cordillera Volcanica Central were represented in the north. Most studies were based on camera traps and focused on the largest felids – jaguar, puma, and ocelot, with little information on the small cats. Jaguar populations occurred at low densities throughout Costa Rica, with apparently little regional variation. Coyotes are invading some areas, and may compete with the smaller felids for prey. The information from this study can provide a valuable tool for setting conservation priorities and environmental policy in Costa Rica. A Introduction Apex predators are the consumers at the peak of the food chain. Their position at the top of the energy pyramid means that they influence the species below them on the pyramid. Their presence is often an indicator of the health of the ecosystem. These apex predators are also keystone species meaning that they have an exceptionally large effect on the function and biodiversity of the ecosystem despite their relatively low abundance (Paine et al. 1995). When they are removed, the entire structure of the ecosystem is changed via a process known as tropic cascades. Trophic cascades refer to the phenomenon where a change in one trophic level leads to alternating positive 294 ARETĒ: The PLNU Honors Journal and negative population changes in the levels below (Polis et al. 2000). When an apex predator is removed, certain species whose populations are limited by their presence, such as medium- and large-sized prey, are able to expand. However, with the large increase in herbivore populations, the plants they eat can then decline dramatically in response to the increased consumption. In this way, the removal of a top predator can completely rearrange an ecosystem (Terborgh et al. 2001). In addition to the idea that apex predators control the species they prey on, there is research that shows that apex predators have an effect on smaller “mesopredators” both by killing these smaller predators and by limiting behaviour and habitat use through fear and competition. When apex predators are removed, these mesopredator populations are no longer controlled, leading to an increase in their distribution and abundance, a phenomenon known as “mesopredator release” (Soule et al. 1988). When these predators increase in abundance, the small animals that they prey on experience a decrease in abundance. This is another way in which the removal of apex predators can have dramatic ecological effects (Ritchie & Johnson 2009). A Case Study: The Wolves of Yellowstone The wolves of Yellowstone present a case study which can be referenced as an example of the removal of a predator from an ecosystem. In the early 1900s the government decided to eradicate wolves from Yellowstone National Park and by 1926 all wolves had been removed (Haines 1996). With the removal of wolves, the elk population exploded. The aspen and cottonwood trees stopped growing due to overgrazing. It wasn’t just the elk and plant populations that were affected. There was also an increase in the number of coyotes and a decrease of several other species including foxes, beavers, and songbirds. Streams began to erode with the loss of grasses to hold the banks firm and there was a decline in the number of amphibian and fish species. Park Rangers began to kill the elk as a means to control the population but these efforts weren’t enough (Stolzenburg 2008). Conservationists and biologists began to talk of reintroducing wolves, but there was a lot of opposition. In 1973 the Endangered Species Act was passed, but it wasn’t until 1995, nearly 70 years after the wolves had been eradicated from the park, that the reintroduction of wolves into Yellowstone began (Phillips & Smith 1997). After the reintroduction of wolves, the park began to return to its original state. With the return of the wolves, both the elk and coyote populations decreased and the populations of aspen, cottonwood, foxes, and other animals began to increase as the park began to flourish once more (“Weaving” 1998). The wolves of Yellowstone are not the only trophic cascade that has been reported. In Zion National Park a study was done by Bill Ripple and Bob Bescha (2006) in which increased human activity in the southern part of the park resulted in the decline and eventual extirpation of cougars. With their disappearance came an increase in the mule deer population as well as a decline in their health and the decline of the health of the rest of the park (Ripple & Beschta 2006). In an experiment done in the intertidal zone, all Pisaster sea stars were removed from one plot and left intact in another. The study saw ARETĒ: The PLNU Honors Journal that the community of invertebrates on the plot with sea stars continued to thrive as it had before the study began while the plot where the sea stars were removed dramatically changed. With the removal of the sea stars the mussel Mytilus californianus took over until is crowded out all the other invertebrates that had previously been found there (Paine 1966). Many other examples are cited in Stolzenburg (2008). Research in Costa Rica Costa Rica is a critical region of connectivity for jaguars and other predatory species as it serves as a bottleneck through which the northern and southern populations are connected. There are several corridors that are maintained throughout Costa Rica to try to allow populations to retain access to one another (“Establecimiento” 2009). Biological corridors are areas of land that are maintained to allow for the movement of animals between fragmented habitats. The reason for concern regarding connectivity is because biological corridors allow for genetic diversity via optimal outbreeding. When it comes time to mate it is important for animals to reach others whom they are not related to ensure that there is a mixing of genes and that the population as a whole stays healthy. Connectivity between populations also provides young with dispersal routes when they are old enough to leave their natal area. In Costa Rica, there are currently over forty corridors that exist on paper (Fig. 1), however less than ten of them are currently being developed by active community committees. Figure 1 - Biological Corridors of Costa Rica. Those highlighted in color are active while those in grey are currently not active (“Establecimiento” 2009). 295 296 ARETĒ: The PLNU Honors Journal Despite the importance of Costa Rica for connectivity of large mammals, there are relatively few studies that have been conducted on the predators in this area. For this reason, our knowledge about the predators in this region is fragmented. Although there are a few published journal articles, many of the studies are in the grey literature. Grey literature includes master theses, technical reports, and community project reports. Because the grey literature is unpublished, it can be difficult for others to access. For this reason we felt it was important to gather all these items into a single comprehensive report that could be made available to the scientific and conservation community in Costa Rica. Having a centralized database can provide a better picture of the conservation issues facing predators in the country as a whole, and better enable scientists and conservations to determine where more research is needed and to make decisions on conservation actions to protect these top predators. The following is a summary of the apex predators found in Costa Rica on which our survey focused: Jaguar (Panthera onca) The jaguar, which is the largest cat found in the Americas, ranges from the southwest US to the Rio Negro in Argentina. They are found in a variety of habitats including rainforest, swamp, grassland, woodland, and deciduous forest and are associated with the presence of water (Caso et al. 2008b). Jaguars hunt a range of prey species but have been found to prefer larger prey such as peccary, marsh deer, and tapir (Hunter 2011). Jaguars face deforestation and fragmentation of forest habitat. They also compete with humans for prey and face persecution, often being shot on sight or hunted by ranchers who fear they will depredate their cattle. Due to these threats, jaguars are currently listed as Near Threatened on the IUCN Red List of Threatened Species (Caso et al. 2008b). Puma (Puma concolor) The puma, the second largest felid in the Americas, has the most extensive range of any terrestrial mammal in the Western Hemisphere and can be found from Canada to the tip of Chile and in every major habitat type, including forests, lowlands, mountains, and desert. In much of Latin America, the puma lives alongside the jaguar and may favor more open habitat than its larger competitor though both can be found in dense forest (Caso et al. 2008d). Although puma are capable of hunting large prey such as peccary and brocket deer, they rely most heavily on small to medium-sized prey such as paca (Hunter 2011). Pumas face the same threats as jaguars (habitat loss, fragmentation, poaching of their prey, and human persecution due to livestock depredation), but are currently listed as Least Concern on the IUCN Red List (Caso et al. 2008d). Ocelot (Leopardus pardalis) The ocelot, a medium-size cat, is generally the most abundant felid in most habitats of the lowland Neotropics and is listed as Least Concern by the IUCN Red List. The ocelot is distributed from Mexico through Central and South America and is found in every country except Chile. There is also a small remnant population of between 80-120 ARETĒ: The PLNU Honors Journal ocelots north of the Rio Grande in the United States. These cats can be found in a variety of habitats including forests, thorn scrub, grasslands and pastures, and coastal marshes (Caso et al. 2008a). The ocelot has been found to negatively impact smaller felids such as margay and oncilla(“the ocelot effect”) (de Oliveira et al. 2010). It eats a variety of small prey species including mammals, birds, and reptiles, but also needs large prey as well, such as peccary and deer. Threats to the ocelot include habitat loss, illegal trade, and retaliatory killing for depredation of poultry (Caso et al. 2008a). Jaguarundi (Puma yagouaroundi) The jaguarondi, another medium-sized cat, is found from Mexico to southern Brazil and south through central Argentina. This felid is found primarily at elevations below 2,000 m but has been reported up to 3,200 m. Research indicates that this is a rare felid. As with other small felids, the jaguarundi is negatively affected by the ocelot. The felid is found in a range of habitats but tends to stay near vegetative cover. The jaguarundi is thought to be mainly terrestrial but can also move about in the trees (Caso et al. 2008c). Its diet consists of mainly small prey such as mice, birds, and fish but occasionally it will take larger prey like armadillo (Hunter 2011). The felid’s main threats are habitat loss and fragmentation but it is also killed for depredation of poultry and may occasionally be caught in traps set for commercially valuable species. The jaguarundi is currently listed as Least Concern by the IUCN Red List (Caso et al. 2008c). Margay (Leopardus wiedii) The margay, a small felid, is declining throughout its range due to the conversion of native forest to agriculture and pasture. It is predicted to decline near 30% over the next 18 years because roads, fire, and deforestation will fragment the remaining populations. The margay is currently listed as Near Threatened on the IUCN Red List, but is predicted to qualify as Vulnerable in the near future. The margay ranges from Mexico through to southern Brazil and Paraguay. This species is generally rare in its range. The margay, like the oncilla, is negatively impacted by ocelots and occurs mainly in areas where ocelot populations are small or absent. Strongly associated with forest habitat, the margay is thought to be the more arboreal than other cat species, as reflected in its long tail. Though it is less tolerant of human presence than the ocelot and oncilla, it will use disturbed areas where there is sufficient tree cover. Threats to the species include habitat loss, fragmentation, roads, illegal trade, and retaliatory killing. The margay is also susceptible to disease outbreaks (Payan et al. 2008). Oncilla or Little Spotted Cat (Leopardus tigrinus) Like the margay, the oncilla is a solitary felid the size of a house cat and is the smallest wild felid in the Americas. Found from Costa Rica to southern Brazil and northeastern Argentina, it generally preys on smaller animals, but can occasionally hunt animals larger than 1 kg. The oncilla is found in a range of habitats but is particularly associated with dense cover. Genetic analysis has found that the subspecies of oncilla from Costa Rica and that of central and southern Brazil have been isolated for approximately 3.7 million 297 298 ARETĒ: The PLNU Honors Journal years and are as genetically distinct as different species in the Leopardus family. More analysis is needed to determine if these populations make up two separate species. If the Costa Rican subspecies (L. t. oncilla) is in fact a separate species, it is likely to be the rarest felid in the Americas. There are few records of the species above 3,000 m. Oncilla are negatively impacted by ocelot and are usually found in areas where ocelot populations are low or absent. The oncilla is listed as Vulnerable on the IUCN Red List and currently faces a variety of threats including habitat loss, fragmentation, illegal trade, and retaliatory killing due to depredation of poultry. The hybridization of this felid with the Geoffroy’s cat and pampas cat may also pose a potential threat (de Oliveira et al. 2008). Coyote (Canis latrans) The coyote, a canid, is distributed throughout North America, Mexico, and Central America. They are abundant and increasing in distribution as human disturbance increases. They are versatile and well-suited to modified environments. Coyote density varies geographically and seasonally but is generally stable throughout its range (HidalgoMihart et al. 2004). Coyotes utilize nearly every available habitat including urban areas, though water availability may be a limiting factor. The coyote is an opportunistic, generalist predator. Its diet is made up of a variety of food ranging from fruit and insects to large ungulates and livestock (though this is often in the form of carrion). In suburban areas they often make use of human-made food resources such as dog food. The coyote is listed as Least Concern on the IUCN Red List and currently faces no threats to its population as the range of this species continues to expand. Hybridization with dogs, grey wolves, and red wolves may be problematic particularly for the Critically Endangered red wolf. The coyote is still sought for its fur and regulations on hunting vary by region (Gese et al. 2008). Grey Fox (Urocyon cinereoargenteus) The grey fox is found in a variety of temperate and tropical regions from Canada through Venezuela and Columbia. Like the coyote it is seen in human occupied habitats although it tends to be found in areas with thick cover such as forest or shrub habitats. Threats to the grey fox include habitat loss, fragmentation, and degradation although it is currently listed as Least Concern on the IUCN Red List (Cypher et al. 2008). Tayra (Eira barbara) The tayra, from the mustelid group, is one of the most common predators throughout its range and is found in natural and disturbed habitats. It occurs from Mexico to northern Argentina with the exception of the high Andes and Caatinga. The tayra is a terrestrial forest species that also makes use of tree habitats and is generally found below 2,000 m. The tayra is an omnivorous species with a diet consisting of fruits, honey, small vertebrates, insects, and carrion. Though its range has been reduced in some areas due to the spread of agriculture, the tayra is able to live at the edges of human settlements and is currently listed as Least Concern on the IUCN Red List (Cuaron et al. 2008). ARETĒ: The PLNU Honors Journal Methods This project was conducted through an exhaustive online and database search including researchers who had available studies. The studies collected included both published studies as well as unpublished studies in the form of technical report and masters theses. The field studies used a variety of different data collection methods including camera trap, track and observation, radio telemetry, scat, and interview studies (Fig. 1). Generally speaking, direct observation of Neotropical predators is not feasible. The elusive nature of these species (often active at night or hidden from people during the day) combined with the dense cover of tropical forests means that direct sightings are rare, and requires that alternative monitoring techniques be employed. The following survey methods were catalogued in our research. The first two techniques can be described as “high-tech” and the remaining methods are “low-tech” (except for fecal genetic analysis). With the exception of radio telemetry, all these methods are non-invasive. The following survey methods were catalogued in our research: Camera Traps Camera traps are cameras equipped with an infrared sensor (“motion detector”) able to capture photos of wild animals without researchers being present. These cameras are used in ecological research and have been gaining more popularity in recent years. They allow researchers to gain information on presence, relative abundance, activity budgets, and sex ratios. Some species have individually unique spot patterns suitable for density estimates. Spotted cats include jaguar, ocelot, margay, and oncilla, although all can be melanistic, while puma, jaguarondi, coyote, and tayra are without distinctive spots. The disadvantage of camera trapping is the cost of purchasing camera units and supplies. Radio Telemetry Radio telemetry is a study method that allows data to be collected at a distance. Typically animals are captured and collared with a device that lets off a continuous signal that can be tracked by a researcher either in the field or via satellite, allowing them to record the movements of the animal. This provides information such as preferred habitat and estimates of home range. The disadvantage is the cost and the need to capture and immobilize study animals, then track them through dense forest. Because animals must be captured and immobilized in order to fit the radio collars, it is a fairly invasive survey method. Tracks Tracks are a low-tech, low-cost method of determining species presence. All it requires is for researchers to go out and identify any tracks they see while in the field. While this method does not provide as much information as some other methods it is useful in compiling species inventories. The disadvantage is that it can be difficult or impossible to distinguish the tracks of similar species, such as the small cats. 299 300 ARETĒ: The PLNU Honors Journal Scat Scat studies are another simple survey technique. Feces found in the field is collected and analysed to determine species identification, and if dissected, it can also be used to determine diet. Traditional scat studies rely on identifying species by the size and morphology of the scat, which can be highly unreliable as there is significant overlap between species. However, new techniques of genetic fecal analysis can extract DNA from intestinal epithelium cells of the predator and identify the sample to both species and individual, thus enabling an estimate of population size. Interviews Interviews are a means of collecting second-hand and retrospective data. This method gives researchers an opportunity to gain information that they are unable to find themselves due to a number of factors (cost, time, etc.) Interviews can provide invaluable information, but may not be as conclusive as other study means. The advantage of interviews is that they can be retrospective, examining historical trends in wildlife abundance that cannot be studied any other way. The disadvantage is that informants may have imperfect memories, or not tell the whole truth (e.g., if they are involved in illegal hunting activities). Results After reviewing all the articles, both published and unpublished, on predators in Costa Rica, a graph of the study methods used in each study was made (Fig. 2). From the graph we are able to see that the majority studies done on predators in Costa Rica were done using camera traps. Figure 2 - A breakdown of the number of each type of study method found The following are locations where predator studies were found in our survey (Fig. 3): Guanacaste Guanacaste Province is located in the northwestern region of Costa Rica along the Pacific Ocean. It borders Nicaragua to the north and is the most sparsely populated province in Costa Rica. Guanacaste is a poorly researched area. Only three studies were ARETĒ: The PLNU Honors Journal found, all of which focused on jaguars. All three confirmed the presence of jaguars while two also provided jaguar density. Cordillera Volcanica Central The Cordillera Volcanica Central is a volcanic mountain range in the central part of Costa Rica that extends from the volcano Turrialba Tapezco to the Pacuare River. This mountainous region is found 60 km north of Costa Rica’s Central Valley, where the capital city of San Jose is situated and 75% of the country’s inhabitants live. Only one study was found for this region. Corcovado National Park Corcovado National Park on the Osa Peninsula is reputed to be the most “biologically intense area in Mesoamerica” according to National Geographic. The Osa Peninsula is located in the southwestern region of Costa Rica in Puntarenas Province on the Pacific Ocean. This area has been relatively well studied over the years. Five studies were found in this region, both inside and outside the park. One was a species inventory and the others tried to gather densities, activity budgets, and sex ratios of specific species. Talamanca Region The Talamanca Cordillera is a region of montane forests in the Talamanca mountains that extends from northwestern Costa Rica to the western region of Panama to the east. The lower-elevation zone of this region has received research attention in recent years. Thirteen studies were found conducted in this area using a variety of survey methods and gathering a range of data including densities, activity budgets, and sex ratios as well as species inventories. Little or no research work has been conducted in the high-elevation region to the west. Figure 3 – A map of the Jaguar Conservation Unities of Costa Rica with areas where studies were found pointed out (Credit: Panthera & Google Earth) 301 302 ARETĒ: The PLNU Honors Journal Below is a map of the areas in Costa Rica where studies were found on predators (Fig. 4). The studies were limited to four main regions, leaving much of the country without any information regarding the presence of predators. Figure 4 – A map of the regions of Costa where studies were found during our survey. Jaguar prints indicate the approximate location of the studies. Presence/Density Presence and density data are available for jaguar in four regions of Costa Rica, but is more limited for the other predators (Table 2). The lower-elevational zone of the Talamanca region has been the best studied in terms of both presence and density with several different predatory species being confirmed present and density found for jaguar, puma, and ocelot. Table 1 - Presence and density of predatory species (Amit et al. 2009a, 2009b, Amit 2006, Gonzalez-Maya et al. 2008a, 2008b, 2008c, 2007, Gonzalez-Maya & Schipper 2008, NavarroArquez et al. 2007, Harvey et al. 2006, Marieb-Zeller et al. 2008, Gonzalez-Maya & CardenalPorras 2011, Pacheco et al. 2006, Blancos 2010, Salom-Perez et al. 2007, Carrillo et al. 2000, Salom-Perez 2005, Salazar 2009, Fernandez et al. 2010) ARETĒ: The PLNU Honors Journal Only the lower elevations of Costa Rica have been well-studied, with no data found on elevations above 2500 meters above sea level (Table 2). The densities for these different elevational zones are variable but cover similar ranges of values. Table 2 – Densities broken down by elevation Sex ratios were only determined for two species (Table 3), jaguar and ocelot, both of which have identifiable markings. The sex ratio determined for jaguars in both Corcovado and the Talamanca region were similar with there being more males per female, however the sex ratio for ocelots showed the opposite trend with more females per male. Note that it can be difficult to reliably assess sex from camera trap photos. Sex Ratio Table 3 - Sex ratios (Gonzalez 2008b, Salom-Perez et al. 2007, Salom-Perez et al. 2005) For the most part the activity patterns found in Corcovado and the Talamanca region are very similar (Table 4). The only notable difference is the puma that is found to prefer nocturnal and dawn hours in Corcovado and tends to be diurnal in the Talamanca region. Activity Table 4 - Preferred times of activity (Salazar et al. 2009, Salom-Perez et al. 2007, Gonzalez-Maya 2008b, 2009) The possible prey species were determined either by being reported present in these locations or having been determined as possible prey species by one of the studies (Table 5). In Corcovado, marine turtle was a prey species not reported elsewhere, as was curassow. In the Talamanca region opossum and rabbit were reported as prey species and were not reported elsewhere in the country. Also of interest is the fact that ocelot has at 303 304 ARETĒ: The PLNU Honors Journal certain times been found in jaguar scat, suggesting that ocelot may be an important prey species to jaguar during certain periods where other prey species are scare. Possible Prey Species Table 5 - Possible prey species for Costa Rican predators (Blancos et al. 2010, Gonzalez-Maya et al. 2008a, 2010, Harvey et al. 2006, Carrillo et al. 2002, 2000, Salom-Perez et al. 2005, Salazar et al. 2009, Salom-Perez et al. 2007) There were only two studies found which tried to estimate the home ranges of predatory species. The home range estimate for jaguars in Corcovado is much larger than the home range estimated in the Talamancas (Table 6). Both studies used the Minimum Convex Polygon method to determine home range; however since this home range estimate uses a limited number of camera traps rather than radio telemetry, the results may not be accurate. Estimated Home Range Table 6 - Estimated home range for predatory species (Gonzalez-Maya et al. 2008a, Salom-Perez 2005) Discussion While twenty-one studies were found, it was still not enough to provide an accurate picture of what is happening throughout Costa Rica. The majority of the studies used camera traps, with a few other methods being applied as well. Only four geographical regions were studied (Guanacaste, Cordillera Volcanica, Osa Penninsula, and the Talamancas), with no information found on other regions. Densities were estimated for a number of species in the Talamancas, but only estimates for jaguars were found in the other two regions. There are several prey species that are found in the Cordillera Volcanica, Osa, and the Talamancas, but there are also several prey species unique to their region, such as marine turtles at Corcovado and ocelot in the Talamancas. There was surprisingly little information about coyotes. They were only reported present in two regions. Coyotes are an invasive species and while they are native some ARETĒ: The PLNU Honors Journal regions of Central America, their populations have been expanding in conjunction with increased human disturbance (Hidalgo-Mihart et al. 2004). Because little research has been done on the species it is difficult to know which areas coyotes are native to and which areas they have moved into recently, or when they moved there. Retrospective interview studies are probably the only way to gather this information. For example, interviews of long-time residents of the Savegre Valley (30 years or more) in 2010 established that coyotes were not present when the valley was first colonized in the 1950s, but arrived sometime in the 1960s after deforestation had started to occur (Mooring et al., 2010). It will be important to establish what effect coyotes are having on native predator species such as small felids, and whether coyotes are competing with these species. The Next Step From this survey, it is clear that there needs to be more research if we are to understand predator populations as a whole in Costa Rica. Even the data from studied areas is incomplete and there are several areas of Costa Rica that haven’t been investigated at all. In addition to surveying more regions, there needs to be focused research on the small cats of Costa Rica as well as the coyote populations in the country. There is almost no information on the small cats, thus we currently do not know how these populations are doing. Also, it is important to survey the coyote populations. Coyotes are native to some areas of Central and South America, but their population is also growing and expanding and moving into areas they have not been before. It is important for conservationists and wildlife managers to know where these coyotes are moving and what affects this spread is having on native species. 1. 2. 3. 4. Conclusions The research that has been done on apex predators in Costa Rica has been limited to four regions, meaning that there is a knowledge gap for much of Costa Rica. In the regions that have been studied, most of the focus has been in the southern region and there are still large gaps in our knowledge at all four sites. The range of jaguar densities was similar in these studied regions. There were 2.86.7 individuals per 100 km2 in Guanacaste, 3.5-7.0 in Corcovado, and 2.4-5.4 in the Talamanca region. Jaguar densities in low- and high-elevation regions also overlapped. Several prey species were found in the study areas. These prey species include agouti, tapir, peccary, and paca. This suggests that these species of are particular importance to predatory species. 305 306 ARETĒ: The PLNU Honors Journal Bibliography Amit, R. 2006. “Densidad de jaguares (Panthera onca) en el Sector San Cristobal del Area de Conservacion Guanacaste, Costa Rica.” Masters thesis, National University, Heredia, Costa Rica. Pp. 55. Amit, R., L. Alfaro & E. 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